Declaration and use of php functions-headlines-php.cn

Declaration and use of php functions

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Release： 2018-06-28 10:02:50

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* Function

* 1. Declaration syntax;

* 2. Calling method;

* 3. Parameter setting;

* 4. Return value;

* 5. Scope

//Declaration

function hello() //无论有无参数,圆括号不能省略
{
    echo &#39;欢迎来到php中文网学习&#39;;
}

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//Call: call by name, must bring parentheses

hello();
echo &#39;<hr>&#39;;
//可以设置参数
function hello1($siteName)
{
    echo &#39;欢迎来到&#39;.$siteName.&#39;学习&#39;;
}

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//You must bring parameters when calling now

hello1(&#39;php中文网&#39;);
hello1(&#39;www.php.cn&#39;);

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//If you forget to give parameters when calling, you can give the function parameters a default value

function hello2($siteName = &#39;php中文网&#39;)
{
    echo &#39;欢迎来到&#39;.$siteName.&#39;学习&#39;;
}
echo &#39;<hr>&#39;;

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//You can pass parameters when calling now , you can also pass no parameters

hello2();
echo &#39;<br>&#39;;
hello2(&#39;PHP中文网_www.php.cn&#39;);

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//If there are multiple parameters, the default value should be written to the end

function hello3($name ,$siteName = &#39;php中文网&#39;)
{
    echo &#39;我是&#39;.$name.&#39;,欢迎来到&#39;.$siteName.&#39;学习&#39;;
}
echo &#39;<hr>&#39;;

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//Calling method

hello3(&#39;peter zhu&#39;); //第一个参数没有默认值,必须传参
echo &#39;<br>&#39;;
hello3(&#39;peter zhu&#39;, &#39;www.php.cn&#39;); //实参与形参的位置必须一一对应
echo &#39;<hr>&#39;;

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//Scope : Function internal variables cannot be accessed from the outside. Similarly, external variables cannot be accessed from inside the function.

$siteName = &#39;php中文网&#39;;

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//External variables, or global variables, will automatically become an element in the global variable array $GLOBALS. The variable is The key name of the element

echo $GLOBALS[&#39;siteName&#39;]; //它里面的数据就是变量siteName中的值,而且这是一个超全局变量,可以在函数中使用
function hello4()
{
    $name = &#39;peter zhu&#39;;
//    return $siteName;
    return $GLOBALS[&#39;siteName&#39;];
}
echo hello4();
echo &#39;<br>&#39;;
echo $name; //外部是访问不到函数内的变量的,除非函数将这个变量返回到外部

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